JavaScript % (modulo) gives a negative result for negative numbers

Question

According to Google Calculator (-13) % 64 is 51.

According to Javascript (see this JSBin) it is -13.

How do I fix this

Answer 1

So it seems that if you're trying to mod around degrees (so that if you have -50 degrees - 200 degrees), you'd want to use something like:

function modrad(m) {
    return ((((180+m) % 360) + 360) % 360)-180;
}